1. Field of the Invention
The present invention relates to an imaging device, such as a digital camera, with which it is possible to generate a bulb shooting image through image combination, and to an imaging device and shooting method capable of displaying a time-lapse image during bulb shooting.
2. Description of the Related Art
In the case of shooting a subject where subject brightness is dark, such as celestial body shooting, shooting methods, such as bulb shooting where exposure is carried out with a prolonged exposure time, are conventionally known. With bulb shooting etc., since it is difficult to set an exposure time to give correct exposure, means are known for successively acquiring divided exposure image data which has been exposed at specified time intervals, and subjecting these divided exposure image data to multiple combination to acquire a single taken image with correct exposure.
Generally, with this type of subject image, since the contrast in subject brightness in the subject image is often large, if the photographer carries out multiple combination on a main subject such as a celestial bodies (stars) so as to achieve correct exposure, there may be situations where correct exposure is not acquired, such as overexposure of subject images other than the main celestial bodies.
There have been various proposals of technology for acquiring correct exposure images with this type of combining of a plurality of images that have been acquired using multiple exposure (refer, for example, to Japanese patent number 4565504 (hereafter referred to as Patent Literature 1), and Japanese patent number 4148586 (hereafter referred to as Patent Literature 2)). In Patent Literature 1 and Patent Literature 2 it is disclosed that divided exposure image data is acquired by carrying out shooting a plurality of times at specified time intervals, and when these divided exposure image data are subjected to image combination processing comparatively bright combination processing is carried out for every divided exposure image data. Here, the comparatively bright combination processing is a technique of comparing pixel data of two images for every pixel, and performing combination processing by selecting pixel data that has the largest brightness output.
With only additive combination of the divided exposure image data, for example, when taking pictures of star trails in celestial body shooting, with normal longer exposure time shooting, in cases where buildings etc. other than the stars exist as a background bright portions of the buildings will be blown out. By contrast, in the case of carrying out comparatively bright combination processing, because simple pixel value addition is carried out, buildings have a fixed brightness and it becomes possible to shoot star trails with correcting exposure for the buildings.